<script>
// 常量：不变的量
// const 常量名=值;

// const  PI=3.1415926
PI=3.14 //报错：Assignment to constant variable.  后期不允许修改值

// const PI;//报错：Missing initializer in const declaration 声明时必须赋值

// 建议常量名大写


// let 所具有的特点  const也有

// console.log(PI);// Cannot access 'PI' before initialization
const PI=3.14

// const PI=3.15;//Identifier 'PI' has already been declared 

{
    const  A="AAA"
}
console.log(A);//A is not defined







</script>